This invention relates to a golf ball, and, more particularly, to a golf ball which is provided with a new and unique dimple pattern which provides excellent distance and accuracy.
This invention represents an improvement over the golf ball dimple patterns which are described in U.S. Pat. No. 4,560,168 and the golf ball dimple patterns which are used on the commercial golf balls sold under the name Wilson Staff and TC.sup.2.
U.S. Pat. No. 4,560,168 describes various icosahedral dimple patterns in which the dimples are arranged so that they do not intersect the six great circles which bisect the sides of the icosahedral triangles. The dimple pattern illustrated in FIGS. 8A and 8B is used on commercial golf balls which are sold under the name Ultra. The Ultra golf ball is a two-piece golf ball which consists of a solid core and a cover. The Ultra dimple pattern includes 432 dimples, and each dimple has the same diameter and depth.
Other figures of U.S. Pat. No. 4,560,168 illustrate using dimples of various sizes on the same ball. The aspect ratio of a dimple is determined by dividing the depth of the dimple by the diameter of the dimple, and column 4, lines 42-45 state that the aspect ratio should be about 0.047 to 0.060, the optimum being about 0.052.
The Wilson Staff golf ball is a three-piece golf ball which includes a solid core, a layer of elastic windings which are wrapped around the core, and a cover. The dimple pattern of the Wilson Staff ball is a 432 dimple pattern which is similar to the Ultra pattern except that there are five different sized dimples and the dimples are frusto-conical rather than spherical. The five dimple diameters are 0.155, 0.150, 0.140, 0.135, and 0.125 inches. The depths of the dimples are 0.0071, 0.0069, 0.0064, 0.0062, and 0.0058 inches, respectively. The aspect ratio for each of the Wilson Staff dimples is therefore 0.046.
The Wilson Staff dimples are frusto-conical rather than spherical, i.e., the side surface of each dimple is formed by the frustum of a cone or a truncated cone rather than by a portion of a sphere. Prior golf balls sold under the name Pro Staff also utilized frusto-conical dimples. The bottom surface of each Wilson Staff dimple is flat and the depth of the dimple is measured to the bottom surface.
A dimple pattern formed by frusto-conical dimples having different diameters and a constant aspect ratio performs satisfactorily when used on a three-piece golf ball such as the Wilson Staff ball. However, such a dimple pattern does not perform satisfactorily when used on a two-piece ball. When the Wilson Staff dimple pattern is used on a two-piece ball having the same construction as an Ultra golf ball, the resulting ball is significantly shorter than the commercial Ultra ball in both carry and total distance (carry plus roll).
However, when the depth of the dimples increases as the diameter of the dimples decreases, a two-piece ball with frusto-conical dimples performs well. The Wilson TC.sup.2 golf ball is a two-piece ball with truncated cone dimples which utilizes that principle.
In the golf ball described in U.S. Pat. No. 4,560,168 and in the Wilson Staff and TC.sup.2 golf balls, the dimples are arranged so that various sized dimples are located throughout the icosahedral pattern. For example, in FIGS. 11A and 11B of the patent the largest dimples are located at dimple positions 3 and 4. In the Wilson Staff and TC.sup.2 balls the largest dimples are located just inside the apexes of the icosahedral triangles.